Autonomously and semi-autonomously controlled machines are capable of operating with little or no human input by relying on information received from various machine systems. For example, based on machine movement input, terrain input, and/or machine operational input, a machine can be controlled to remotely and/or automatically complete a programmed task. By receiving appropriate feedback from each of the different machine systems during performance of the task, continuous adjustments to machine operation can be made that help to ensure precision and safety in completion of the task.
Earthmoving machines such as track type tractors, motor graders, scrapers, and/or backhoe loaders, have an implement such as a dozer blade or bucket, and need continuous adjustment for their operations. For example, the dozer blade or bucket must be adjusted on a worksite in order to alter a geography or terrain of a section of earth. The implement may be controlled by an operator or by a control system to perform work on the worksite such as achieving a final surface contour or a final grade on the worksite. The determination of an absolute 3-D position of the implement cutting edge (e.g., blade cutting edge) is critical for the implement to achieve the desired results.
Conventionally, an implement control system may include a 3-D positioning sensor (e.g. a Global Positioning System (GPS)) attached to the chassis of the machine. In this configuration, actuator position sensors measure displacement of the implement actuators (e.g. hydraulic cylinders) and these sensor outputs are used to calculate the position of the implement cutting edge with respect to the machine chassis (i.e. in a local coordinate frame). Such calculations are, however, highly dependent on precise calibration of the actuator position sensors.
U.S. Pat. No. 6,253,160 to Hanseder (“the '160 patent”) discloses an arrangement for calibrating a tool positioning mechanism. The tool positioning mechanism includes a plurality of encoders, which indicate the position of the tool (e.g., a bucket). The encoders are calibrated by mounting a first GPS antenna on the tool and resolving a vector between the first antenna and a second antenna mounted on another portion of the chassis of the machine. Calibration is accomplished by setting the outputs of the encoders to a predetermined value, such as a full-range, which is measured using the vector when the tool is fully extended.
While the '160 patent may provide a useful way to calibrate a tool positioning mechanism, precise calibration may be challenging because the tool positioning mechanism may only work if the machine is placed on a flat surface, which would be difficult if the calibration has to be done in the field.
The implement position control system of the present disclosure is directed toward solving one or more of the problems set forth above and/or other problems of the prior art.